<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>登录3</title>
  <style>
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }

    body {
      height: 100vh;
      background-color: aquamarine;
      background: url("https://images.pexels.com/photos/936722/pexels-photo-936722.jpeg?auto=compress&cs=tinysrgb&w=1260&h=750&dpr=1") no-repeat;
      background-size: cover;
    }

    .Box {
      position: fixed;
      top: 50%;
      left: 50%;
      transform: translate(-50%, -50%);
      width: 550px;
      height: 330px;
      display: flex;
    }

    .left {
      position: relative;
      width: 50%;
      height: 100%;
      background-color: rgba(57, 99, 134, 0.75);
    }

    .right {
      position: relative;
      width: 50%;
      height: 100%;
      background-color: rgba(255, 255, 255, 1);
    }

    .centerBox {
      position: absolute;
      top: 50%;
      left: 50%;
      transform: translate(-50%, -50%);
      width: 80%;
      text-align: center;
    }

    .left img {
      width: 50px;
      height: 50px;
      margin-bottom: 5px;
    }

    .left p {
      font-size: 14px;
      color: #fff;
    }

    .left h4 {
      font-size: 18px;
      color: #fff;
      margin-bottom: 10px;
    }

    .right form {
      position: absolute;
      top: 50%;
      left: 50%;
      transform: translate(-50%, -50%);
      width: 80%;
      text-align: center;
    }

    h3 {
      margin-bottom: 20px;
    }

    input {
      width: 100%;
      height: 30px;
      border: 1px solid #767676;
      background-color: transparent;
      padding-left: 10px;
      font-size: 12px;
      color: #000000;
      margin-bottom: 15px;
      outline: none;
    }

    .loginBtn {
      width: 100%;
      height: 35px;
      line-height: 32px;
      text-align: center;
      font-size: 15px;
      color: #fff;
      border-radius: 6px;
      background: rgb(57, 99, 134);
      outline: none;
      border: none;
      margin-top: 10px;
    }

    .no {
      cursor: pointer;
      margin-top: 30px;
      text-align: center;
      font-size: 12px;
      color: #828282;
    }
  </style>
</head>
<body>
<div class="Box">
  <div class="left">
    <div class="centerBox">
      <img src="https://img0.baidu.com/it/u=2804005887,994501744&fm=253&fmt=auto&app=138&f=JPEG?w=200&h=200"
           alt="">
      <h4>某某后台管理系统</h4>
      <p>This is a description</p>
    </div>
  </div>
  <div class="right">
    <form action="">
      <h3>欢迎登录</h3>
      <input type="text" placeholder="请输入账号" required>
      <input type="password" placeholder="请输入密码" required>
      <input type="submit" class="loginBtn" value="登录"></button>
      <p class="no">没有账号？立即注册</p>
    </form>

  </div>
</div>
</body>
</html>